1. Field of the Invention
The present invention relates to an image data computing apparatus for computing three-dimensional image data on the basis of a plurality of two-dimensional image data acquired at different times, in order to make an ultrasonic diagnosis or the like.
2. Description of a Related Art
Heretofore, in order to obtain a three-dimensional image in an ultrasonic diagnosis or the like, it has been composited by acquiring a plurality of two-dimensional sectional images. Each of the two-dimensional sectional images is obtained by compositing a plurality of pixel data acquired in time series while a one-dimensional sensor array with a position sensor is kept scanning an object to be inspected. Further, the three-dimensional data is obtained by interpolating sections on the basis of the plurality of two-dimensional sectional images.
With this technique, however, time lags are involved in the scanning direction of the sensor array, so that the sectional images at different times are composited. Besides, the positions of the sensor are monitored, and the images are composited on the basis of the positional information, so that the composite image becomes obscure. Accordingly, the technique is not suitable for the image composition in which an organism is handled as the object to be inspected as in the ultrasonic diagnosis.
In order to solve the above problems, a two-dimensional sensor array should desirably be employed for the obtainment of a three-dimensional image. Considered by way of example is a method wherein an ultrasonic signal is acquired as the two-dimensional image of light by employing an optical fiber array. With this method, a plurality of ultrasonic images can be acquired at some time points on the basis of ultrasonic signals which enter the two-dimensional sensor array after the lapse of predetermined time periods from the transmission of a certain ultrasonic wave. The resulting two-dimensional data, however, are the mixed data of all the ultrasonic signals entering after the predetermined time periods have lapsed from the transmission and do not directly express data at a specified point on three dimensions.
Meanwhile, proceedings xe2x80x9cRinshoo-Hooshasen (Clinical Radiation)xe2x80x9d Vol. 43 No. 11 (published in 1998 by Kanehara and Co., Ltd. in Tokyo) contains a report xe2x80x9cA Principle of Three-Dimensional Displayxe2x80x9d written by Tsuyoshi Mochizuki. It is stated in the report that a conventional data collection method wherein an ultrasonic scanning section is successively moved requires a long time till the acquisition of the whole set of data, so it cannot obtain an accurate image in case of handling a moving object. As one solution to the drawback, a data collection method which employs a movable array vibrator of two dimensions is mentioned, and a method which displays the surface and internal information items of an object at the same time is introduced as a direct method. It is also stated, however, that hardware and signal processing inevitably become large scales in the present circumstances.
The present invention has been made in view of the problems as explained above. An object of the present invention is to provide an image data computing apparatus which computes three-dimensional image data on the basis of a plurality of two-dimensional image data acquired at different times by employing a two-dimensional sensor array.
In order to accomplish the object, an image data computing apparatus according to the first aspect of the present invention is an apparatus for computing three-dimensional image data on the basis of detection data obtained by transmitting an ultrasonic wave from transmission means toward points to be measured, which exist in a three-dimensional space, and detecting the ultrasonic wave reflected from the points to be measured by use of a two-dimensional sensor array including a plurality of sensors, and comprises: a line memory having a plurality of lines for storing the detection data obtained on the basis of output signals of said plurality of sensors respectively for a predetermined time period; storage means for storing as a table therein transfer time period data determined by relations between distances from the transmission means to the respective sensors through the respective points to be measured and transfer velocities of the ultrasonic wave in corresponding paths; and computation means for reading the detection data stored in said line memory in accordance with the transfer time period data stored in said storage means for the respective points to be measured, and for computing image data at the respective points to be measured on the basis of the read detection data.
Besides, an image data computing apparatus according to the second aspect of the present invention is an apparatus for computing three-dimensional image data on the basis of detection data obtained by transmitting an ultrasonic wave from transmission means toward points to be measured, which exist in a three-dimensional space, and detecting the ultrasonic wave reflected from the points to be measured by use of a two-dimensional sensor array including a plurality of sensors, and comprises: a line memory having a plurality of lines for storing the detection data obtained on the basis of output signals of said plurality of sensors respectively for a predetermined time period; storage means for storing as a table therein transfer time period data determined by relations between distances from the transmission means to the respective sensors through the respective points to be measured and transfer velocities of the ultrasonic wave in corresponding paths, and weighting factors for the detection data; and computation means for reading the detection data stored in said line memory in accordance with the transfer time period data stored in said storage means for the respective points to be measured, and for computing image data at the respective points to be measured by adding the read detection data after multiplying them by the weighting factors stored in said storage means for the respective points to be measured.
According to the present invention, three-dimensional image data can be computed on the basis of a plurality of two-dimensional image data acquired at identical sensor positions at different times by employing a two-dimensional sensor array. Accordingly, a clear three-dimensional image can be obtained even in an ultrasonic diagnostic apparatus which is directed toward organisms.